Examining pathogenic Vibrio abundance and environmental controls across macroalgae, sediment, and oysters

Climate change is accelerating the geographic spread and abundance of pathogenic Vibrio species in coastal waters, posing growing threats to ecosystems and human health. We investigated the abundance and pathogenic gene presence of V. vulnificus and V. parahaemolyticus across three common estuarine substrates (macroalgae, sediment, and oysters) in a temperate estuary. Macroalgae consistently harbored the highest Vibrio counts in conjunction with elevated pathogenic gene frequencies, while oysters contained the lowest. Environmental conditions related to Vibrio abundance were substrate and Vibrio species specific. Temperature and salinity were most closely related to pathogenic Vibrio abundance in oysters. In contrast, pathogenic Vibrio abundance on macroalgae and within surface sediments was most closely related to water column nutrient concentrations, chlorophyll-a, and total suspended solids (TSS). Recognizing the different, substrate-specific environmental conditions related to pathogenic Vibrio abundance is critical for predicting risks, improving water quality models, and public health in a changing climate.

Pathogenic Vibrio bacteria are ubiquitous in marine and estuarine environments and can cause severe human illness, yet ecological understanding and risk assessments often focus primarily on oysters in Vibrio monitoring due to their relevance in seafood safety. However, oysters represent only one of the many environmental niches of Vibrio in coastal ecosystems. This study revealed that within this coastal system, macroalgae harbored higher Vibrio concentrations. Additionally, we demonstrate that pathogenic Vibrio abundance on macroalgae, oysters, and sediments is each related to distinct environmental conditions.